1.Field
The present invention generally relates to an LCD device, an electronic apparatus and an electronic system, and more particularly to an LCD device having a pixel electrode and a pixel driving transistor.
2.Description of Prior Art
With advantages of lightweight and low electricity power consumption, LCD devices are used as monitors for the electronic apparatus such as a computer or a mobile phone. In an active matrix display device which employs the thin film transistors (TFT) for applying voltages to the pixels electrodes, the TFTs are positioned between the data lines and the pixels electrodes. The gate lines are utilized to switch the aforesaid TFTs and provide the voltages which are applied to data lines to the pixels electrodes as disclosed in Japan Patent Publication No. 2007-188079.
For extending the service lifespan of the LCD device, the applied voltages between the pixel electrodes and the common electrode are inverted for each frame to force the voltages applied to the liquid crystals to be inverted correspondingly in the LCD device. Meanwhile, non-inverted and inverted voltages can be applied to the scan lines in one frame to control the liquid crystals not to be merely twisted toward a single direction.
Please refer to FIG. 16, which shows waveforms of gate line driving method of an embodiment according to prior arts. FIG. 16(A) shows waveforms of a first liquid crystal driving status and FIG. 16(B) shows waveforms of a second liquid crystal driving status. The solid lines represent gate voltages Vg, Vg′. The dotted lines represent source voltages Vs. Vs′. The one-dot chain lines represent drain voltages Vd, Vd′. The two-dot chain lines represent a common voltage Vcom applied to a common electrode.
In the gate line driving method of the prior arts as shown in FIG. 16, the gate voltage Vg is unrelated to the first liquid crystal driving status or the second liquid crystal driving status but a fixed value. Therefore, when the gate voltage Vg becomes the base voltage Vgl as the TFT is turned off in the first liquid crystal driving status as shown in FIG. 16(A), the voltage difference between the base voltage Vgl of the gate voltage Vg and the drain voltage Vd is 2.3V. However, in the second liquid crystal driving status shown in FIG. 16(B), the voltage difference between the base voltage Vgl′ of the gate voltage Vg′ and the base voltage Vsl′ of the source voltage Vs′ is increased up to 7.5V. Consequently, the difference of the off-status currents Ioff of the TFT exists between the first liquid crystal driving status and the second liquid crystal driving status. Significantly, the difference of the off-status currents Ioff between the first liquid crystal driving status and the second liquid crystal driving status is one of the reasons causing the picture quality deterioration and causing a flicker phenomenon on the screen.